This invention relates generally to heat resistant articles, and, more particularly, to an ablative surface for protecting a base material from the deleterious effects of extreme heat.
There has long existed a need for an insulation which will protect a base material from oxidation and erosion while exposed to a very hot gaseous fluid and which itself is mechanically and chemically able to withstand high temperatures and protect the base material from thermal shock while it is withstanding rapid and extensive changes in temperature. Such an insulation, if provided, would be of much value when employed as a high temperature furnace lining, a protective covering for a heat treating rack or a lining for a rocket nozzle, etc.
The insulation may be in the form of an ablative surface, that is, one which chars and wears away because it is exposed to high temperature or is moving at high speed in relation to a fluid with which it is in contact. In wearing away, the ablative surface prevents frictional heat from destroying the base material on which it is deposited, by utilizing several heated-transfer mechanisms.
Certain elastomeric moldable materials (which form pyrolitic chars) such as Dow Corning 93-104 or General Electric RTV-1300 can provide this type of thermal protection. The problem, however, is that the high interface temperature between a combustion chamber structure, for example, and the insulative materials negates the use of conventional chemical adhesives when the interface temperature exceeds 700.degree.F. This situation occurs since chemical adhesives pyrolitically decompose between 400.degree. and 700.degree.F.